Younger Patients with CLL/SLL Are Less Frequent and Have Favorable Survival in a Canadian Population Based Study: The Manitoba Cohort.

Background: Detailed population-based clinical characteristics and outcomes of chronic lymphocytic leukemia (CLL) and small lymphocytic leukemia (SLL) are scarce. We have previously demonstrated in the province of Manitoba that by combining population-based sources of a cancer registry and a centralized flow cytometry database, the incidence of CLL/SLL is much higher than previously reported. We have now examined the clinical characteristics of this large and well defined patient group. We hypothesized that the clinical features of these patients (pts) may differ from previous studies where data was obtained from referral centers.

Methods: All pts from the Manitoba Cancer Registry with ICD codes 9 & 10 for CLL or SLL from 01/01/1998 to 12/31/2003 were identified. Pts from the flow cytometry database during this time period with a diagnosis of CLL/SLL were also identified. A retrospective electronic chart review was conducted. The two databases were compared and analyzed.

Results: 715 pts with CLL were identified. 358 pts were identified from the cancer registry alone, 136 pts by the flow cytometry database, and 221 pts in both datasets. Overall, the age-adjusted annual incidence rate of CLL/SLL in Manitoba was 10.5/10⁵ (95% C.I. 9.4–12.7/105). Median age of all pts was 72yrs (19–101). Only 71 pts (9.9%) were aged <55 and 212 pts (29.6) were <65. The Male: Female ratio was identical in the age<55 and >55 categories (1.33). Median follow-up of living pts is 6.6 years (range 2.0–8.0). The Cox regression model was used to evaluate the significance of prognostic factors including age at diagnosis and gender. Older cases (>55 years) had significantly higher risk of dying (HR: 4.0, 95%CI: 1.23–13.1) than younger pts. Women had a slightly lower risk of dying (HR: 0.78, 95%CI: 0.40–1.50) than men. For the 136 pts for whom accurate Rai staging was available, estimated median survival has not been reached in stage 0 patients, while it was 7.2 years in stage I–II cases and 4.5 years in stage III–IV patients. Cause specific mortality and complete survival according to Rai stage for all pts will be presented at the meeting.

Conclusions: In this population-based CLL/SLL cohort, clinical presentation and outcomes appear to differ from previously reported studies. Specifically, (1) there are fewer younger pts, (2) the male: female ratio is similar amongst all ages, (3) older pts have a significantly poorer survival, (4) pts with advanced Rai stages appear to live longer than previously reported. This has important implications for treatment and counseling of pts, as well as for resource allocation for this common hematological malignancy.